We want to maximise the amplification of the primordial spectrum between CMB scales and the end of inflation, and this may be achieved while being in the weak dissipative regime with \(Q<1\)  when observational constraints applied, but ending inflation in the SDR. Searching for this pattern motivates our choice of the dissipative coefficient and the inflationary potential. However, it must be stressed that WI all the way along in the SDR can provide a viable scenario to overcome the difficulties to have inflation (i.e. quasi de Sitter vacua) in string theory [1]}, [2]}, [3]}, [4]}, as given by the so-called swampland conjectures [5]}, [6]}, [7]}, [8]}, [9]}. These demand the relative slope of scalar potentials to be larger than one in Planck units, i.e. having standard slow-roll parameters \(\epsilon _\phi ,\, |\eta _\phi | \gtrsim 1\) , which invalidates slow-roll cold inflation. On the other hand, in WI those parameters are only required to be smaller than a factor \((1+Q)\) , i.e., they can be larger than one in the SDR. Several examples of this can be found in the recent literature, depending on the combination of inflationary potential and particle interactions leading to dissipation: although a linear dissipative coefficient with a quadratic chaotic potential as in the WLI model is consistent with observations only for values \(Q_* \lesssim 1\)  [10]} at horizon-crossing, we can reach \(Q_* \simeq O(100)\)  with Higgs-like potentials [11]}; and a cubic dissipative coefficient as in MWI [12]} gives \(Q_* \simeq O(100)\)  when combined with a hybrid-like potential. In addition, the “Transplanckian Censorship Conjecture” [13]}, [14]} sets an upper bound on the scale of inflation \(V^{1/4} \simeq 3 \times 10^{-10} m_P\) , in both cold and warm inflation [15]}, [3]}. This could be achieved with runaway potentials, but the SDR-WI version has the advantage of being already consistent with the other swampland conjectures [17]}, [18]}, and solve the problem of the graceful exit [19]}.
